need advice for making a very custom water gun

Build a homemade water gun or water balloon launcher and tell us about it.
neogeo
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Re: need advice for making a very custom water gun

Post by neogeo » Sun May 16, 2010 7:30 pm

I've had some time these past couple of days to work on the soaker, and I have to say that this is a bit harder than I anticipated. I modded the PC with 4 layers of bike tire tubing, temporarily reconnected the PC case via a couple of screws, and hooked the lines up to everything for a preliminary test. The results were mixed.

Overall, it showed me that there's a few underlaying problems with the materials I'm using. All of the connections were made with T-joints, teflon tape, and hose clamps. Apparently, I either did not add enough teflon tape to the joints, or that method is simply inadequate to make a solid, leak free connection. Nearly all of the joints leak currently, mostly the two connections between the PC and the pump, and the lines out to the water valves and nozzles. I think it may be due to not having enough teflon tape on the joints because after adding a few extra turns to a couple of the joints, they stopped leaking. Also, due to either the leaks or the fact that poly tubing expands a bit under pressure, I have yet to have the system actually hit 65 PSI. Every single one of my pressure tests ended either when a connection leaked very badly or a line burst off of a joint. The PC case seems to be able to hold the PC as of right now, but I'm still probably going to switch to a PVC case nearer to the end of this.

Other things I've noticed are that when partially pressurized, there's no difference is shot length when having one or both nozzles firing at the same time. Although, at higher pressures, the stream tends to break up more readily. Also, with 4 layers of tubing over the PC, the pump takes much longer to pump it up as fully as I've been able to get it. It's not a major inconvenience, but I'd say it's around 10 seconds from empty to "full" as it stands right now. I most likely won't add anymore layers of bike tubing to the PC.

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C-A_99
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Re: need advice for making a very custom water gun

Post by C-A_99 » Mon May 17, 2010 2:32 am

I'm not really seeing the necessity of a pressure rated PC case here. If the LRT hits the PC case and gets forcibly pumped at that point, it will burst either way. I guess pressure rated pipe would not expand from that force as cellcore pipe might, but either way I don't see how the pipe would burst apart dangerously.

For the threads, you should be using at least 3-5 layers of teflon tape and the threads should be tightened fairly well. Be extremely careful for metal to plastic threads because the plastic threads can break. For hose clamps, they must be tightened sufficiently especially for LRT. Wrap some electrical tape or other protection around the LRT before clamping it to avoid tearing, or you'll need special clamps that won't tear into the tube.

Using higher diameter tubes for the pump to PC connection may allieviate the pumping problem, to a certain point anyways.

Also, layered balloons were, or should have been suggested earlier as a solution for the PC. They are the best alternative if you cannot get LRT, if it's too expensive, or if you can't get bike tubes to work well. Just some reference for the future if you need to replace the PC.

neogeo
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Joined: Mon Apr 26, 2010 4:01 pm

Re: need advice for making a very custom water gun

Post by neogeo » Fri May 21, 2010 3:33 am

Well, some good news and some bad news. The bad news is that my PC case exploded on me today. It exploded right where I thought it would, which was where I drilled the holes for the screws. The actual PC is still fine though. The good news is that I learned some things, and have made some changed to my design.

First, I am going to go with a PVC PC case now. I'm pretty much forced to, as the regular one will never be able to take the pressure. I read that the piece of PVC I bought is rated for up to 200 PSI, which is far and away more than I'll put into this gun. Speaking of PSI, I opened up the case on my garden sprayer and was surprised to find out that the cutoff for the pump is actually 80 PSI, not the 65 that was posted on the box. This might explain why my joints continue to fail. I'm using upwards of 15 layers of teflon tape and it's just not helping. I think I'll have to go to flare fittings and brass T-joints next. It's what I should've done from the beginning, but I thought it'd be overkill. Guess there's not really such a thing with this project.

Right now, work has stagnated until I can get the system pressure stable. That's going to require modifying the clamp on the end of the PC to accept the PVC tubing, figuring out some way to secure the flair fittings or the tubing to the smooth ends of the nozzles and PC valve assembly, and ensuring that there's no leaks in the system. Once that's done, I can begin integrating the system with my servos, microcontroller, and mounting plates.

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C-A_99
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Re: need advice for making a very custom water gun

Post by C-A_99 » Fri May 21, 2010 4:08 am

Well on second thought, I guess a pressure rated PVC case wouldn't be such a bad idea now. I wasn't assuming overpumping to be a problem though.

I'm rather surprised that the thread are still leaking. It's possible that the threads have been damaged and are not going in straight, as that was the cause for some leaking I had to deal with previously.

neogeo
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Re: need advice for making a very custom water gun

Post by neogeo » Sat May 22, 2010 3:53 am

Yeah, it might be. Where I seem to be having the most trouble is with the straight bits of tubing that are at the ends of the water valves and the PC clamp. I guess it's because it's straight and smooth, instead of barbed like the T-joints. The T-joints do leak a bit up at the higher end of the pressure scale, but the smooth joints leak much sooner. I'm honestly kind of stumped on how to get them to attach to the hose tightly.

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zeda.beta
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Re: need advice for making a very custom water gun

Post by zeda.beta » Sat May 22, 2010 5:01 pm

Have you tried PVC welding yet? That prevents almost all of the leaks on any gun.
-Zeda
I reject your reality and substitute my own.
Quack damn you.

neogeo
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Re: need advice for making a very custom water gun

Post by neogeo » Sat May 22, 2010 11:04 pm

I'm not sure is PVC welding would work for whatever plastic the SS elements are made of to vinyl tubing. Would any glue or sealant work in tangent with the teflon tape and hose clamps? Alternatively, are there any other types of connections that I'm forgetting? Would something like, say, a quick-connector work for the pressures I'm facing? I know those are used more for stiffer tubes like those elements.

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zeda.beta
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Re: need advice for making a very custom water gun

Post by zeda.beta » Sun May 23, 2010 1:09 am

Gorilla Glue or super glue should work well, because gorilla glue expands as pressure is put on it during drying.
-Zeda
I reject your reality and substitute my own.
Quack damn you.

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C-A_99
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Re: need advice for making a very custom water gun

Post by C-A_99 » Sun May 23, 2010 2:50 am

Gorilla Glue does not seal at all and is weaker than epoxy.

If the leaks are minor, epoxy or epoxy putty would be a possible permanent solution, though that's an unusual way to get it to seal.

neogeo
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Re: need advice for making a very custom water gun

Post by neogeo » Sun May 23, 2010 3:12 am

The nozzles only leak a tiny bit, but the PC mechanism can get a good sized spray going at the higher pressures. Of course, that may be due to fewer layers of teflon tape, as I never really bothered to count exactly how many wraps I did.

What about regular pipe sealant that you can buy at some hardware stores? Or would that be a waste of money? As far as glue/epoxy goes, what if I were to, say, slather the whole end of the tube in glue before pushing the softer tubing onto it? Then just apply a hose clamp and let it dry. I think that was where Zeda was going with it anyway.

neogeo
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Re: need advice for making a very custom water gun

Post by neogeo » Wed May 26, 2010 1:49 am

I think I may have solved all my leak problems. I went and bought some compression fittings. I also bought some copper tubing that is ever so slightly larger than the inserts on those fittings to ensure that the fitting works properly. The t-joints are now water tight at pressure. I also think that same typer of fitting could work on the ends of the SS components as well. I have to buy some straight connectors and try though. The diameter of the plastic tips looks about the same size as the inserts I have. If they are, I just have to slip a piece of tubing over them and voila, instant Leak-B-Gone.

Of course, that's assuming it all works right, and we know how well that's been working for me so far.

neogeo
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Re: need advice for making a very custom water gun

Post by neogeo » Tue Jun 01, 2010 8:42 pm

I wonder if anyone's following this. I know work's going slow, but it tends to do that when you've got two jobs and only one or so days a week to work on it. Hopefully, this thing'll be done this month. :-/

Anyway, in case anyone's still reading this, I got the compression fittings working yesterday and went to see if I could get the system to full pressure. I could hear the pump slowing down and getting ready to shut off and there weren't any leaks in sight, until one of the nozzles decided to spring a massive leak. Like, one of the seals ruptured and sprang a good foot-and-a-half spraying leak.

Now who didn't see that coming a mile away?

Anyway, I guess I'm off to go look for some cheap solenoid valves. Does anyone have any ideas on where to get some that can withstand up to 80 PSI and run on 12V for as cheap as possible? There were the ones posted back a page or two in the thread, but those were like $75, which is far and away out of my price range right now. Oh, also, I've preemptively switched the PC mechanism from the original plastic one to an all brass one. Once those solenoid valves are in place, the only two points of failure left will be the tubing itself, and the PC itself exploding for some reason.

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soakernerd
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Re: need advice for making a very custom water gun

Post by soakernerd » Sat Jun 05, 2010 10:41 pm

Are these cheap enough for you?
solenoid valves
I got to their site by using google shopping for "12v solenoid valve" there are many pertinent hits for under $20.

neogeo
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Re: need advice for making a very custom water gun

Post by neogeo » Sun Jun 06, 2010 12:03 am

Actually, that looks exactly like it might work! I googled the same terms yesterday, but didn't find this for some reason. Now I just need to work out some sort of nozzle for it and I'll be set.

One other thing I've been wondering if I should do is install a cutoff switch inside the PC case. The cutoff switch would just turn the pump off when the PC gets full and pushes the switch. It would be more work, but it'd act as a secondary safety to help prevent case blowouts and overpressurization. What do you guys think?

EDIT: Wow, I need two solenoid valves and the site only has one in stock. If that just ain't my luck. :(
Last edited by neogeo on Sun Jun 06, 2010 12:11 am, edited 1 time in total.

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soakernerd
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Re: need advice for making a very custom water gun

Post by soakernerd » Sun Jun 06, 2010 3:31 am

This one is 24v, but it might work. otherwise, the cheapest I could find was this

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